1. Field of the Invention
The invention relates to the field of trailers having means for loading, unloading and transporting containers between locations such as storage terminals, job sites, dumping depots and the like. The invention concerns a trailer that carries two containers in line, and in particular provides a loading/unloading mechanism for a forward container that is distinct from that used for the rear container and includes a follower device whereby the front container can be moved to the rear container position.
2. Prior Art
Trailers for transporting removable containers between job sites, storage terminals, dumping depots and the like are known in industries such as the refuse and/or solid-waste/sludge handling industry, the intermodal shipping industry, etc. The trailers are towed by tractors, and are outfitted with hydraulic or electric systems for loading, unloading, or otherwise handling the removable containers. The trailer may be deployed, for example, to take an empty refuse container from a storage terminal to a job site where the container is left behind for the collection of refuse, solid waste and like material, and a full container may be removed and taken to a dumping depot, or back to the storage terminal, and so on.
It is known to provide a trailer of this kind with an undercarriage carrying a tilt frame. Tilt frames are movable between a level position for transport and an inclined position for loading and unloading from the rear of the trailer. In its inclined position, the tilt frame defines a ramp onto which a container resting on the ground can be hoisted, whereupon the tilt frame is lowered back to its level position for stably transporting that container over the road. To unload the container from the trailer, the tilt frame is tilted again to allow the container to slide off, as controlled by resistance offered by a taut cable and winch arrangement or the like.
For handling containers that are shorter than the trailer, means can be provided to carry two or more containers in line, head to toe. In a stretched trailer for plural containers, only the rear portion of the trailer needs to be tiltable for loading and unloading. The trailer bed typically has a front half defining a front docking position and a rear half defining a rear docking position. Mechanisms are provided to move a container forward or backward between the docking positions when the tilt frame is down.
Thus, the first container on a double container trailer is hoisted up the ramp of the tilt frame from the back end of the trailer. To do this, the tilt frame is inclined. A cable is attached to the container. The container is pulled up the inclined tilt frame by a hydraulic cylinder or hydraulic winch coupled to the cable. The tilt frame is lowered to the level position. The first container is then moved forward into the front docking position, clear of the tilt frame, which can be tilted again to pull up the second container. The second container is taken on in generally the same fashion and using the same pulling apparatus as before, but is not moved any farther forward than the rear docking position on the tilt frame.
Whereas there are two containers to be handled, and the front one needs to be moved forward and backward to clear the tilt frame, there are complications in the driving structures needed. Known double container trailers use various methods to move the first container between the front and rear docking positions (onto or off of the horizontally disposed tilt frame). Such methods may employ as many as three driving systems, each with an independent cable arrangement mounted at a different point on the trailer and terminating in a connector end attachable to one or the other of the containers at one end or the other. For instance, one cable system hoists the container up the inclined ramp of the tilt frame (and eases it down by gravity when unloading). In view of the power needed to pull a full container up the incline, a relatively powerful hydraulic mechanism may be needed. The cable is pulled from a point at the forward end of the tilt frame, e.g., at a pulley or winch, such that the container is drawn up to that point. After the tilt frame is moved to horizontal, the first cable is detached and a second cable is attached for moving the container forwardly, beyond the pulley or the like from which the first cable was pulled. This cable system pulls from the front of the front docking position to pull the container into place. A third system also is needed, namely to move the forward container from the front docking position to the rear docking position. This system pulls from the rear, or perhaps pushes from the front.
The fact that one portion of the trailer must tilt while the other is stationary, the different directions in which force must be applied, and the different endpoints from which force is applied, all contribute to the complexity of the hydraulic or other driving means, with the result being that the operator must tend to the attachment, detachment and stowing of various cables. It would be advantageous to achieve the necessary displacements of the containers without the need to attach and detach so many cable systems. These operations waste an operator's time, and increase the danger of the operation.